Many staplers are known of the type comprising a housing having a passageway extending from an inlet opening to an outlet opening, which passageway is adapted to guide a single open staple from the inlet to the outlet opening; means for biasing a stack of open staples into the inlet opening; a ram slidably mounted on the housing for movement between a load position spaced from the inlet opening to afford movement of one of the open staples into the passageway, along the passageway with an end portion of the ram pushing the staple to an eject position at which the staple has been pushed to the outlet opening; and a manually activated drive mechanism for propelling the ram from its load to its eject position in opposition to biasing means. Typically, portions of the ram cover the inlet opening to prevent another staple from being fed into the passageway as the ram moves a staple in the channel toward the outlet opening, and means are provided for preventing movement of the ram back to its load position before it has moved fully to its eject position. Without such means, if the drive means was not completely activated to cause the ram to eject the staple from the outlet opening the ram could return to its load position under the influence of the biasing means, a second staple could enter the passageway, and upon subsequent activation of the drive mechanism the two staples in the passageway could jam the stapler.
While many prior art devices have been devised to prevent such double feeding, many are not as simple, inexpensive, or reliable as is desired.